Printing apparatus and correction data generating method

1. A printing apparatus comprising: an exposing head comprising a plurality of light emitting elements arranged in a primary scanning direction whose luminance are separately controllable, said exposing head and a photosensitive material being movable relative to each other in a secondary scanning direction perpendicular to said primary scanning direction, said light emitting elements being controllable, during the relative movement of said exposing head and said photosensitive material, based on set exposure data to generate a test chart; a scanner for scanning said test chart to acquire scanning data; and a correction data generating means for setting correction data regarding the luminance of said light emitting elements based on said scanning data; wherein said scanner has a resolution capable of acquiring density of a plurality of areas formed by dividing, in the primary scanning direction, each of pixel lines on said test chart corresponding to the respective light emitting elements; wherein said correction data generating means performs: a pixel identifying process for identifying said pixel lines corresponding to said light emitting elements from said scanning data; a density data acquiring process for acquiring density data of a plurality of areas adjacent a middle position in the primary scanning direction of each of the pixel lines, among the plurality of areas arranged in the primary scanning direction for each of the pixel lines identified in said pixel identifying process; and a correction data generating process for generating said correction data based on the density data acquired in said density data acquiring process.

2. The printing apparatus of claim 1 , wherein said density data acquiring process is performed for each of a plurality of scanning areas in different positions in the secondary scanning direction on said pixel lines, said correction data generating means being set to generate said correction data by averaging density data of said plurality of scanning areas acquired in the process performed by said density data acquiring process.

3. The printing apparatus of claim 2 , wherein a total number of scanning areas is set, for setting a ratio of noise included in the density data of said pixel lines, to be at most a predetermined numerical value and a product of the number of areas arranged in said primary scanning direction and the number of said scanning areas is set to a value at least equal to said total number of scanning areas.

4. The printing apparatus of claim 1 , wherein said light emitting elements have even numbers and odd numbers assigned thereto along a direction of formation; said test chart comprises an even-number pixel area having a plurality of pixel lines formed by exposure at the light emitting elements having the even numbers assigned thereto, an odd-number pixel area having a plurality of pixel lines formed by exposure at the light emitting elements having the odd numbers assigned thereto, and an all-pixel area having a plurality of pixel lines formed by simultaneous exposure at the light emitting elements having the even numbers and the odd numbers assigned thereto; said pixel identifying process is operable to identify said plurality of light emitting elements based on the pixel lines in said even-number pixel area or said odd-number pixel area of said test chart; and said density data acquiring process is operable to acquire density data of the pixel lines in said all-pixel area present on extensions in the secondary scanning direction of the pixel lines identified in said pixel identifying process based on the pixel lines in said even-number pixel area or said odd-number pixel area.

5. The printing apparatus of claim 1 , wherein said exposing head comprises fluorescent light emitting tubes, each having a plurality of light emitting elements arranged in the primary scanning direction and capable of emitting light independently of one another.

6. A correction data generating method for use in a printing apparatus with an exposing head having a plurality of light emitting elements arranged in a primary scanning direction whose luminance are separately controllable, moving said exposing head and a photosensitive material relative to each other in a secondary scanning direction perpendicular to said primary scanning direction, generating a test chart by controlling each of the light emitting elements of said exposing head, during the relative movement of said exposing head and said photosensitive material, based on set exposure data, and setting correction data to regarding the luminance of each said light emitting element from scanning data acquired by scanning the test chart with a scanner; wherein said scanner has a resolution capable of acquiring density of a plurality of areas formed by dividing, in the primary scanning direction, each of pixel lines on said test chart corresponding to the respective light emitting elements; said method comprising the steps of: identifying said pixel lines corresponding to said light emitting elements from said test chart acquired with said scanner; acquiring density data of a plurality of areas adjacent a middle position in the primary scanning direction of each of the pixel lines, among the plurality of areas arranged in the primary scanning direction of each of the pixel lines identified in the step of identifying said pixel lines; and generating said correction data regarding the luminance based on the density data determined in the step of acquiring density data.